Lead Zirconate Titanate Fine Fibers Derived from Alkoxide-Based Sol-Gel Technology

Fine-scale fibers with diameters <100 µm were prepared using metal alkoxide precursors. Variables that influence fiber drawing and fiber properties in the lead zirconate titanate (PZT) compositional system were investigated to obtain the processing conditions necessary to fabricate high-quality fibers. The gel-to-ceramic conversion was characterized. In addition to drying, firing cycles at temperatures >650°C were needed to achieve phase-pure perovskite fibers. Dense fibers with diameters of 10-70 µm and grain sizes <1 µm were found with sintering temperatures up to 1000°C. Increasing the firing temperature to 1200°C for 30 min resulted in grain growth up to 2.5 µm. Electrical properties of both lanthanum-doped and undoped PZT fibers were measured and were comparable to bulk disks fabricated using powder derived from the same sol.     

Thermal degradation of PTFE studied by ultraviolet photoelectron spectroscopy (u.p.s.)

The early stages of the thermal degradation of PTFE were followed by ultraviolet photoelectron spectroscopy in order to evaluate the technique and to establish the effects of changes in molecular weight and sample thickness, also γ-irradiation and copolymerization on the degradation reaction. The rate of decomposition and the concentration—time profile for the evolution of monomer from homopolymers was that predicted for a first order reaction, and depended on sample weight and area. Copolymers and γ-ray irradiated samples showed some differences in products and rates.     

Analysis of acoustic emissions from polymers

Acoustic emissions obtained from polymers under stress have been subjected to various mathematical analyses with the objective of relating the observed signals to accompanying chemical and physical changes in the polymer. The following methods have been investigated: frequency analysis, autocor-relation analysis, cepstrum analysis and cluster analysis (pattern recognition). It is shown that it is possible to classify the signals from a given polymer sample into relatively few types and that there is a periodicity in a number of plots of acoustic power vs time. Differences between samples are evident, although it is not possible at this stage to state that they are statistically significant. The materials examined include, nylon-6,6, ‘Diakon’, polypropylene and various composites.     

SH3BP2 Deficiency Ameliorates Murine Systemic Lupus Erythematosus

Background: The adaptor protein Src homology 3 domain-binding protein 2 (SH3BP2) is widely expressed in immune cells. It controls intracellular signaling pathways. The present study was undertaken to investigate the role of SH3BP2 in a murine systemic lupus erythematosus model. Methods: For the lupus model, we used Fas^lpr/lpr mice. Clinical and immunological phenotypes were compared between Fas^lpr/lpr and SH3BP2-deficient Fas^lpr/lpr mice. Splenomegaly and renal involvement were assessed. Lymphocyte subsets in the spleen were analyzed by flow cytometry. To examine the role of SH3BP2 in specific cells, B cell-specific SH3BP2-deficient lupus mice were analyzed; T cells and bone marrow-derived dendritic cells and macrophages were analyzed in vitro. Results: SH3BP2 deficiency significantly reduced lupus-like phenotypes, presented as splenomegaly, renal involvement, elevated serum anti-dsDNA antibody, and increased splenic B220⁺CD4⁻CD8⁻ T cells. Notably, SH3BP2 deficiency in B cells did not rescue the lupus-like phenotypes. Furthermore, SH3BP2 deficiency did not substantially affect the characteristics of T cells and macrophages in vitro. Interestingly, SH3BP2 deficiency suppressed the differentiation of dendritic cells in vitro and reduced the number of dendritic cells in the spleen of the lupus-prone mice. Conclusions: SH3BP2 deficiency ameliorated lupus-like manifestations. Modulating SH3BP2 expression could thus provide a novel therapeutic approach to autoimmune diseases.     

Constraint and exploitation of redundant degrees of freedom during walking

What kind of leg trajectories are selected during human walking? To address this question, we have analyzed leg trajectories from two points of view: constraint and exploitation of redundant degrees of freedom. First, we computed the optimal leg swing trajectories for forward and backward walking that minimize energy cost for the condition of having some stretch of elastic components at the beginning of the leg swing and found that the optimal trajectories explain the characteristics of measured trajectories. Second, we analyzed how and when leg joints cooperate to adjust the toe position relative to the hip position during walking and found that joint coordination (i.e., joint synergy) is exploited at some control points during human walking, e.g., the toe height when it passes through its lowest position from the ground and the leg posture at the beginning of the double-support phase. These results suggest that the basic constraint in selecting a leg trajectory would be the minimization of energy cost; however, the joint trajectory is not strictly controlled over the entire trajectory and redundant degrees of freedom are exploited to adjust the foot position at some critical points that stabilizing walking.     

Fabrication of Transparent Grain‐Oriented Polycrystalline Alumina by Colloidal Processing

Grain‐oriented polycrystalline alumina (PCA) ceramics with very high, nearly single‐crystal transparency were successfully fabricated through colloidal processing in a high magnetic field followed by hot isostatic pressing. The c‐axis of the produced material was oriented along the direction parallel to the magnetic field. The transmittance of the specimen with a thickness of 0.8 mm was 78% at a wavelength of 650 nm, close to the reported value of 84.5% for sapphire and more than 10% higher than the largest transmittance magnitude ever reported for PCA ceramics. In addition, the Na salt of 4,5‐dihydroxy‐1,3‐benzenedisulfonic acid (named “Tiron”) was found to be a highly effective dispersant for processing high‐purity materials.     

Vegetation dynamics of Zimbabwe investigated using NOAA-AVHRR NDVI from 1982 to 2006: a principal component analysis

The dominant modes of vegetation variability over Zimbabwe are investigated using principal component analysis (PCA) on National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) normalized difference vegetation index (NDVI) monthly imagery from 1982 to 2006. Spectral analysis is also used to determine the periodicities of the component loadings. NDVI PCA-1 corresponds to the major vegetation types of Zimbabwe, and we demonstrated that grasslands and dry savannah have the strongest relationship with mean annual precipitation. Furthermore, the March–April loadings showed the highest correlation (r?=?0.73) with mean annual precipitation. NDVI PCA-1 sheds some light on the land reform challenge in Zimbabwe. NDVI PCA-2 is highly correlated (r?=?0.87) with the mean annual relative variability of the rainfall map indicating a southeast/north mode of anomalies associated with the convectional rainfall-bearing systems over Zimbabwe. NDVI PCA-2 is also highly correlated (r?=?0.86) with precipitation PCA-2. NDVI PCA-3 shows a southeast/west mode and is highly correlated (r?=?0.87) with precipitation PCA-3. A high correlation (r?=?0.66) is also noted between NDVI PCA-4 and the elevation map. Spectral analysis of the PCA loadings revealed several periodicities corresponding to those found in tropical sea surface temperatures (SSTs).     

Effects of Glass Additions on (Zr,Sn)TiO4 for Microwave Applications

The effects of glass additions on the properties of (Zr,Sn)TiO₄ as a microwave dielectric material were investigated. The (Zr,Sn)TiO₄ ceramics with no glass addition sintered at 1360°C gave Q = 4900 and K = 37 at 7.9 GH_z. Several glasses, including SiO₂, B₂O₃, 5ZnO–2B₂O₃, and nine commercial glasses, were tested during this study. Among these glasses, (Zr,Sn)TiO₄ sintered with ZnO-B₂O₃–SiO₂ (Corning 7574) showed more than 20% higher density than that of pure (Zr,Sn)TiO₄ sintered at the same temperature. A 5-wt% addition of SiO₂, to (Zr,Sn)TiO₄, when sintered at 1200°C, gave the best Q : Q = 2700 at 9 GHz. Results of XRD analysis and scanning electron microscopy and the effect of glass content are also presented.